For the sake of ornament, and to prevent the wall from being injured by chairs knocked up against it, a moulded bar, called a "chair rail," is sometimes fixed at a height of about 3 feet from the floor, and parallel to the skirting.
This rail should be fixed to a narrow horizontal ground, and should be wide enough to cover the grounds and their junctions with the plastering.
The interval between the rail and the skirting is called the Dado, D in Fig. 162, and the chair rail, SB, is called the "surbase" of the dado - the skirting forming the "base " B, or, as it is some times called, the plinth.
Fig. 161. Scale, 1 inch = l foot.
The dado may be either panelled, simply boarded, or formed only by the surface of the plastered wall, as in Fig. 162.
Fig. 162 shows a chair rail or surbase, SB, and plastered dado, D, with wooden "base" or "skirt-ing," B.
The chair rail and the upper moulding of the skirting are nailed to narrow grounds, g g, Fig. 162, fixed to plugs inserted in the wall.
A portion of the skirting is broken away to show the blockings, bk, supporting it as described at page 80.
Fig. 162. Scale, ½ inch = l foot.
The dado illustrated in Fig. 163 is entirely of wood, being formed of wide boards, grooved and feathered, and hung by thin tongues of hard wood, j, at intervals of about 3 feet, to the narrow ground, g, which supports the surbase, SB. The boarding is strengthened and kept together by taper keys, k, similar to that described at page 75.
The keys may be about 3 feet apart.
The boarding of the dado is thus suspended from the upper "ground," and is free to expand and contract without opening the joints.
Fig. 163. Scale, 1 inch = l foot.